I know this is completely unsupported..

But is there any chance someone here tried using Airtime as a "dj software" and broadcast to Centova?

I'll keep my opinion on this idea to myself but to give you something to check out: Could work using relaying.

If Airtime supports sourcing ShoutCast DNAS streams then you can just turn off the autoDJ in Centova Cast -- it'll function like a standard ShoutCast live source.

If it doesn't support sourcing DNAS then there's nothing that could be done short of working out the format of their audio stream and building some kind of transcoding solution.  That'd require hiring a developer and would likely have a substantial price tag attached.